A standard width for window assemblies is approximately three and one-half inches. This relatively standard width lends itself well to installation of window assemblies in buildings having wall supporting frames built with two by four studs, because any openings for windows are framed by studs that are three and one-half inches wide. On the other hand, this relatively standard width does not lend itself particularly well to installation in buildings having wall supporting frames built with two by six studs, because any openings for windows are framed by studs that are five and one-half inches wide. Nonetheless, economies of scale often discourage the production of five and one-half inch wide window assemblies, perhaps because the bulk of demand for windows to date has been in connection with two by four construction. Thus, a need exists to facilitate installation of three and one-half inch wide window assemblies into openings framed by five and one-half inch studs or jambs in a manner that is attractive and cost effective.